Do you still have any Recovery discs?
Is the Product Key on the laptop base clear enough to read and copy?
Is there stuff on the lappy that you need? (Files, folders, Photos, music, videos etc.)
Can you transfer these to an external source? (External Hdd/another PC/DVD's, whatever.)
I have a 3+ years old DV7 and I recovered all my stuff to a USB key and Double-layer DVD, before writing down the Product Key and using another Windows 7/64 bit disc, to carry out a fresh install of Windows. Then I reinstalled all my programmes and other stuff.
This has the added bonus of removing all the HP software, which is frankly garbage. It speeds up your machine, if the Hdd and all other hardware is OK it will seem like a new lappy.
I think as a precaution you also need to look at a possible infection. If you get it back to working order, download an Internet Security product, check with Malware Bytes. Even Microsoft Security Essentials will help.
I wrote this post before seeing the others - follow their advice FIRST.